1. Field of the Invention
This invention relates to bending of glass plates moving in a horizontal or approximately horizontal position, under the effect of their own weight, with a device including a shaping bed made of rotating shaping elements whose surfaces in contact with the glass plates, as they advance, define increasingly curved generatrices, these shaping elements being mounted on a frame that is adjustable in height and can be inclined in the lengthwise direction of movement of the plates, by pivoting around a transverse horizontal axis located at the upstream end of the shaping bed. The rotating shaping elements of the shaping bed can have various configurations. The disclosure of this application is related to the U.S. patent application Ser. No. 669,872, filed on the same date as the present application by the present Applicants and entitled "BENDING OF GLASS SHEETS ON SHAPING BED CONSISTING OF ROTATING ELEMENTS".
2. Description of the Prior Art
It is known to have rigid rollers with a curved profile, mounted to rotate, as shown in U.S. Pat. No. 4,139,359.
It is also known to have rotating rods or cylindrical rollers that are sufficiently flexible and elastic to be deformed by the inclination of their ends in relation to the horizontal and so that this modification of shape is compatible and is maintained with the rotation. Such deformable rollers are described, for example, in U.S. Pat. No. 4,226,608.
In another known bending device, the rotating shaping elements also participate in the conveying and are formed by flexible tubular sheaths rotatably driven around rigid curved rods. Adjustment of the radius of curvature of the bending shape, and the progression of its curvature in the direction of conveying the glass plates is achieved by the fact that the various curved rods are mounted so as to be able to be pivoted around an axis that passes through their ends, and so they can be adjusted to inclinations that are different from one another, which increasingly removes them from the conveying plane in which the glass plates are located when they arrive.
Such a bending device is described in detail in French Pat. No. 2,312,463. In this prior device, the shaping elements, i.e., curved rods surrounded by their rotating tubular sheaths, are mounted on a frame hinged at its upstream end on a stationary pivoting axis located at the level of the cylindrical conveying rollers of the preceding installation that brings the glass plates to the device. While each curved rod can be more or less inclined to cause a variation of the radius of curvature which each element that it contains exhibits to the underside of the glass plates, the frame that supports the assembly of shaping elements is able to pivot around the transverse axis located at its upstream end so that the summits of the curvatures of the shaping elements always remain at the level at which the flat plane glass plates are introduced in the bending device.
It is thus possible for both convex and concave shaping beds to maintain the central line at the summit of the sheets of glass at the same level during the bending operation.
However, when to meet certain conditions, it is desired to perform the bending so that the lengthwise edges of the glass sheets extending parallel to the conveying direction remain at the same level, this is possible with the known device for only a determined width of glass plates. When glass plates of another width have to be bent, the position of their lengthwise edges on the shaping elements is necessarily different and the level of these edges is necessarily lower or higher, which acts on the optical quality of the curved glass plates and can affect them unfavorably.